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utils.js
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utils.js
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const abi = require('ethereumjs-abi');
const util = require('ethereumjs-util');
const BN = require('bn.js')
//============================================================================
// PUBLIC FUNCTIONS
//============================================================================
const constructPaymentMessage = async function (contractAddress, balance) {
return abi.soliditySHA3(
["address", "uint256"],
[new BN(contractAddress, 16), balance]
);
}
const signMessage = async function (web3, message, accountAddress) {
return await web3.eth.personal.sign(
`0x${message.toString("hex")}`,
accountAddress
);
}
const isValidSignature = async function (contractAddress, balance, signature, expectedSigner) {
let message = await constructPaymentMessage(contractAddress, balance);
let prefixedMessage = await prefixed(message);
let signer = await recoverSigner(prefixedMessage, signature);
return signer.toLowerCase() === util.stripHexPrefix(expectedSigner).toLowerCase();
}
//============================================================================
// INTERNAL FUNCTIONS
//============================================================================
async function prefixed(hash) {
return abi.soliditySHA3(
["string", "bytes32"],
["\x19Ethereum Signed Message:\n32", hash]
);
}
async function recoverSigner(message, signature) {
let split = util.fromRpcSig(signature);
let publicKey = util.ecrecover(message, split.v, split.r, split.s);
let signer = util.pubToAddress(publicKey).toString("hex");
return signer;
}
export default {
constructPaymentMessage,
signMessage,
isValidSignature
}